There is now good evidence that prostaglandins (PGs) are involved in both mammalian and avian reproduction. The main objective of this proposal is to study the functional role of PGs in the reproductive processes of the hen with particular reference to the metabolism of arachidonate and the mode of action of PGs in the control of oviposition. Experiments will be conducted to identify the physiologically key PGs of the arachidonic acid cascade by measuring the rate of PG synthesis during the ovulatory cycle using radiochromatography, RIA and bioassay techniques such as platelet aggregation and muscle superfusion. Particular attention will be paid to the possible role of key intermediates: PG endoperoxides, thromboxanes and the recently discovered prostacyclin. To gain information on the mode of action of PGs in the avian shell gland (SG) a) binding of PGs to various membrane fractions will be characterized; b) effects of PGs on the phosphorylation of specific proteins in such membranes will be studied and c) the studies will be correlated with the cyclic hormonal changes during the ovulatory cycle, focusing on the interrelationship between PGs, steroids and neurohypophyseal hormones. Furthermore, the hypothesis that PGs play a role in calcium mobilization from the medullary bone of the skeleton during intensive shell calcification will be tested experimentally. Finally, the role and action of PGs in follicular rupture will be studied using both in situ and in vivo approaches.